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BUG: KASAN: vmalloc-out-of-bounds in fb_write_offset drivers/video/fbdev/core/sysmem.h:30 [inline]
BUG: KASAN: vmalloc-out-of-bounds in fb_bitmap_2ppw drivers/video/fbdev/core/fb_imageblit.h:364 [inline]
BUG: KASAN: vmalloc-out-of-bounds in fb_bitmap_imageblit drivers/video/fbdev/core/fb_imageblit.h:462 [inline]
BUG: KASAN: vmalloc-out-of-bounds in fb_imageblit drivers/video/fbdev/core/fb_imageblit.h:492 [inline]
BUG: KASAN: vmalloc-out-of-bounds in sys_imageblit+0x19fb/0x1d60 drivers/video/fbdev/core/sysimgblt.c:24
Write of size 8 at addr ffffc900052910a0 by task syz.0.17/6037

CPU: 3 UID: 0 PID: 6037 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
 fb_write_offset drivers/video/fbdev/core/sysmem.h:30 [inline]
 fb_bitmap_2ppw drivers/video/fbdev/core/fb_imageblit.h:364 [inline]
 fb_bitmap_imageblit drivers/video/fbdev/core/fb_imageblit.h:462 [inline]
 fb_imageblit drivers/video/fbdev/core/fb_imageblit.h:492 [inline]
 sys_imageblit+0x19fb/0x1d60 drivers/video/fbdev/core/sysimgblt.c:24
 drm_fbdev_shmem_defio_imageblit+0x20/0x130 drivers/gpu/drm/drm_fbdev_shmem.c:39
 soft_cursor+0x524/0xa10 drivers/video/fbdev/core/softcursor.c:74
 bit_cursor+0xd3a/0x14e0 drivers/video/fbdev/core/bitblit.c:370
 fbcon_cursor+0x43c/0x5e0 drivers/video/fbdev/core/fbcon.c:1433
 hide_cursor+0x87/0x230 drivers/tty/vt/vt.c:883
 do_con_write+0x220c/0x4ae0 drivers/tty/vt/vt.c:3304
 con_write+0x23/0xb0 drivers/tty/vt/vt.c:3664
 do_output_char+0x63b/0x850 drivers/tty/n_tty.c:418
 process_output drivers/tty/n_tty.c:482 [inline]
 n_tty_write+0x4e6/0x1200 drivers/tty/n_tty.c:2377
 iterate_tty_write drivers/tty/tty_io.c:1008 [inline]
 file_tty_write.isra.0+0x4ca/0x8f0 drivers/tty/tty_io.c:1056
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6af/0x1050 fs/read_write.c:687
 ksys_write+0x12a/0x250 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1e9d59f559
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffef6339e58 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f1e9d825fa0 RCX: 00007f1e9d59f559
RDX: 0000000000001006 RSI: 0000200000000e00 RDI: 0000000000000005
RBP: 00007f1e9d636b20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1e9d825fac R14: 00007f1e9d825fa0 R15: 00007f1e9d825fa0
 </TASK>

The buggy address belongs to a vmalloc virtual mapping
Memory state around the buggy address:
 ffffc90005290f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90005291000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>ffffc90005291080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
                               ^
 ffffc90005291100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90005291180: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
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